The invention relates to a wide-viewing angle liquid crystal display, and more particularly to a wide-viewing angle liquid crystal display providing omnidirectional viewing angle characteristics.
Liquid crystal displays (LCDs) have many advantages over other conventional types of displays including exceptional picture quality, small volume, light weight and lower power consumption. LCDs, for example, have been used for several years as displays in, personal digital assistants (PDAs), portable computers, mobile phones, and the like. Nevertheless, LCDs suffer from poor viewing angle characteristics.
In order to improve the viewing angle characteristics, various proposals have been made. Recently, an MVA (Multi-domain Vertical Alignment) type LCD was proposed by Fujitsu Co. Ltd. of Japan. FIGS. 1A and 1B are cross-section views showing the operation of a conventional MVA-LCD. FIG. 1A shows the state of liquid crystal molecules inside the LCD when no external electric field is present or the electric field presence is lower than a threshold value. The color filter (CF) glass substrate 100 and the thin film transistor (TFT) glass substrate 102 are parallel to each other. Protrusions 104 and 106 are formed on the inner surface of both the CF glass substrate 100 and the TFT glass substrate 102. Liquid crystal molecules 108 having negative dielectric anisotropy (referred to in the following as negative type liquid crystal molecules 108) are vertically aligned between the CF glass substrate 100 and the TFT glass substrate 102, constituting a liquid crystal layer 110. Liquid crystal molecules 108 close to the protrusions 104 and 106 tilt in specific direction due to local elects and resulting in pre-tilts.
FIG. 1B shows the state of liquid crystal molecules inside the LCD when an electric field above a threshold value is present. Due to the strong electric field, orientation of the negative type liquid crystal molecules 108 is changed such that directors of the liquid crystal molecules 108 are aligned in a direction vertical to the electric field. Hence, within the same pixel, liquid crystal molecules 108 on each side of the protrusion will tilt oppositely and have different molecular alignment. The protrusions 104 and 106 within a pixel divide the pixel into two or more domains. In other words, a multi-domain pixel is formed improving the viewing angle of LCD.
FIG. 2 is a schematic top view showing a conventional MVA-LCD with a W-shaped protrusion structure. The conventional MVA-LCD comprises a plurality of pixel units 210 defined by crossing bus lines. The protrusions 104 with a first W-shaped pattern are formed on the CF substrate 100. The protrusions 106 with a second W-shaped pattern are formed on the TFT substrate 102. The first and second W-shaped patterns are alternately positioned. A common line 220, serving as an electrode for the storage capacitor Cs, passes through the middle portion of each pixel unit 210. Through the alternately positioned protrusions 104 and 106 on the inner surfaces of different glass substrates of a pixel unit 210, each pixel unit 210 is divided into four different domains. The liquid crystal molecules 108 inside the conventional MVA-LCD tilt in four specific directions, providing viewing angle characteristics that are not omnidirectional and are thus inferior, particularly in the direction which is about ±45° and ±135° to the bus lines.
U.S. Pat. No. 6,532,054 to Ohmuro et al., the entirety of which is hereby incorporated by reference, describes a liquid crystal display having excellent display characteristics. FIGS. 16 and 17 of the reference show protrusion patterns are not extended in one direction, whereby alignment directions of the liquid crystal molecules are approximately omnidirectional.